This invention relates generally to control input devices, and more specifically to control input devices using non-contacting magnetic devices and sensors.
In the field of work machines, particularly those machines which perform digging or loading functions such as excavators, tractors, backhoe loaders, and front shovels, the work implements are generally manually controlled with two or more operator controls in addition to other machine function controls. The manual control system often includes foot pedals as well as hand operated levers. There are several areas in which these types of implement control schemes can be improved to alleviate operator stress and fatigue resulting from the manipulation of multiple levers and foot pedals. For example, a machine operator is required to possess a relatively high degree of expertise to manipulate and coordinate the multitude of control levers and foot pedals proficiently. To become productive an inexperienced operator requires a long training period to become familiar with the controls and associated functions.
Some manufacturers recognize the disadvantages of having too many control levers and have adapted a two lever control scheme as the norm. Generally, two vertically mounted levers, such as joysticks, share the task of controlling the linkages (e.g., boom, stick, and bucket) of the work implement. For example, Caterpillar excavators employ one joystick for stick and swing control, and another joystick for boom and bucket control.
One disadvantage of many joysticks, particularly with digital joysticks, is the use of contacting switches. For example, joystick contacting switches are used to control direction of movement. However, such switches are subject to wear, necessitating switch replacement or repair. Other joysticks use potentiometers, or mechanical means to control the direction of movement. These types of joysticks, however, are typically of low reliability. Thus, the long term cost of the above joysticks may be quite high. Further, when a joystick is not operating properly, the machine often cannot be used. This xe2x80x9cdown-timexe2x80x9d greatly adds unacceptable burdens to the machine owner/lessor due to time restrictions on most jobs.
Several attempts have been made to overcome the problems of contact-type joysticks with non-contacting technology. For example, some non-contacting control handles use inductive sensors for detecting the displacement of a control shaft from a neutral position. However, such inductive sensors are susceptible to electromagnetic interference, are complex to manufacture, and require expensive drive circuitry for operation.
Another type of non-contacting joystick uses hall effect devices to detect the position of the control shaft from a neutral position. However, some hall effect devices have problems similar to the inductive sensors discussed above. Further, many hall effect joysticks typically require complicated design and manufacturing for the placement of magnets and sensors, such as mounting the magnets on counterbalances, or requiring other complex mounting schemes. As the complexity of the input device increases, so does its cost. In addition, the likelihood of failure/breakdown increases with the complexity of the design.
The present invention provides apparatus for transmitting a signal corresponding to a rotation of a spherical body. The apparatus includes a housing having an aperture, and a substantially spherical body having a first portion disposed within the housing so as to have a portion of the body disposed within the aperture, the spherical body being operable to rotate within the housing. A first and second permanent magnets are disposed within the spherical body, and are operable to emit a magnetic field. A first magnetic sensing device is disposed within the housing, the first magnetic sensing device operable to detect the magnetic fields and to generate a first output signal as a function of the strength of the magnetic fields. The first output signal is transmitted via a first conductive path coupled with the sensor.